The present invention generally relates to semiconductor processing, and in particular to a system and method for detecting defects on or in various films employed in semiconductor processing.
In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there has been and continues to be efforts toward scaling down the device dimensions (e.g., at submicron levels) on semiconductor wafers. In order to accomplish such high device packing density, smaller and smaller features sizes are required. This may include the width and spacing of interconnecting lines, spacing and diameter of contact holes, and the surface geometry such as corners and edges of various features.
The requirement of small features with close spacing between adjacent features requires high resolution photolithographic processes. In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the resist, and an exposing source (such as optical light, x-rays, etc.) illuminates selected areas of the surface through an intervening master template, the mask, for a particular pattern. The lithographic coating is generally a radiation-sensitive coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive image of the subject pattern. Exposure of the coating through a photomask causes the image area to become either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer.
Due to the extremely fine patterns which are exposed on the photoresist, defect reduction becomes critical. Furthermore, as the patterns continue to decrease in size, the defect size of interest also decreases. That is, when feature sizes were large, the size of defects in a particular film had to exceed a minimum threshold to be of concern to the process designer. Now, however, the value of the minimum defect size threshold has substantially deceased, and the design of systems and methods for detecting such small defects has become extremely difficult.
It is therefore desirable to have a system and/or method which is capable of effectively and reliably detecting defects in various films employed in semiconductor manufacturing.
The present invention is directed toward a system and method of detecting a film or substrate composition or a defect within a known film or substrate using a scanning probe microscope employing a nanotube tip.
According to one aspect of the present invention, a scanning probe microscope is used to scan a film or substrate of interest. The scanning probe microscope employs a unique scanning tip formed of a nanotube such as a carbon nanotube. The carbon nanotube has a material encapsulated therein or coated thereon which exhibits a characteristic based on the film or substrate composition being scanned at the scanning tip. By monitoring the tip during the scanning process, the composition of the film or substrate may be identified as well as any defects located therein.
According to another aspect of the present invention, a carbon nanotube scanning probe microscope tip has a material which exhibits a fluorescence (e.g., a fluorophore) based on the composition of the film or substrate being scanned. For example, a light source such as a laser is focused on the carbon nanotube tip during scanning to excite the material therein. The fluorescence which emanates therefrom is a function of the film or substrate composition under the tip. For example, the fluorescence intensity or wavelength is detected and used as a signature to identify the film or substrate composition. By scanning the tip across the film or substrate sample, a defect or composition profile may be readily ascertained by evaluating changes in the tip fluorescence.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.